Here is a non-blowback paintball pistol that you can use for self defense. The Mercury Rise MUB .43 Caliber Pistol has a semi-auto firing mode. It has a velocity adjuster from 280 to 370fps and an effective range of 30 meters. It uses 8gram Co2 cartridges.
The Mercury Rise MUB has a 4-round magazine and high impact polymer trigger frame. It comes with a Picatinny rail for your accessories. You can use this to shoot pepper balls, paintballs, and rubber balls.